java map对象的效率比较

import static java.lang.System.out;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Hashtable;
import java.util.IdentityHashMap;
import java.util.Iterator;
import java.util.LinkedHashMap;
import java.util.LinkedList;
import java.util.List;
import java.util.Map;
import java.util.Stack;
import java.util.TreeMap;
import java.util.Vector;
import java.util.WeakHashMap;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.CopyOnWriteArrayList;
import org.apache.commons.collections.FastArrayList;
import org.apache.commons.collections.list.TreeList;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.time.StopWatch;
@SuppressWarnings("unchecked")
public class MapPerformance {
public static void main(String[] args) {
MapPerformance test = new MapPerformance(10 * 10000);
out.print(StringUtils.center("Test Map Performance: loop=" + test.loop, 80, '-'));
out.printf("\n sssssss", "", "put", "put", "remove", "get",
"iterator","for");
test.benchmark(new HashMap());
test.benchmark(new Hashtable());
test.benchmark(new LinkedHashMap());
test.benchmark(new IdentityHashMap());
test.benchmark(new TreeMap());
test.benchmark(new WeakHashMap());
test.benchmark(new ConcurrentHashMap());
}
private int loop = 10000;
public MapPerformance(int loop) {
this.loop = loop;
}
public void benchmark(Map map) {
out.printf("\n s", map.getClass().getSimpleName());
int j;
StopWatch watch = null;
//1.测试顺序性能(Add)
(watch = new StopWatch()).start();
for (int i = 0; i < loop; i++) {
map.put(i, i);
}
watch.stop();
out.printf("d", watch.getTime());
//2.测试随机插入性能(Random insert)
(watch = new StopWatch()).start();
for (int i = 0; i < loop; i++) {
j = (int) (Math.random() * loop);
map.put(j, new Integer(-j));
}
watch.stop();
out.printf("d", watch.getTime());
//3.测试随机索引删除(Random remove)
(watch = new StopWatch()).start();
for (int i = 0; i < loop; i++) {
j = (int) (Math.random() * loop);
map.remove(j);
}
watch.stop();
out.printf("d", watch.getTime());
//4.测试随机取数性能(Random get)
(watch = new StopWatch()).start();
for (int i = 0; i < loop; i++) {
j = (int) (Math.random() * loop);
map.get(j);
}
watch.stop();
out.printf("d", watch.getTime());
//6.测试迭代性能(Iterator)
(watch = new StopWatch()).start();
Iterator<Object> iter = map.values().iterator();
while (iter.hasNext()) {
iter.next();
}
watch.stop();
out.printf("d", watch.getTime());
//7.测试迭代性能(Iterator)
(watch = new StopWatch()).start();
// Iterator<Object> iter = list.iterator();
for (Object obj : map.values()) {
}
watch.stop();
out.printf("d", watch.getTime());
}
}

结果：

-----------------------Test Map Performance: loop=100000------------------------
put random-put remove get iterator for
HashMap 47 94 78 47 0 0
Hashtable 141 78 78 62 0 16
LinkedHashMap 125 78 94 47 0 0
IdentityHashMap 172 265 47 63 15 16
TreeMap 94 125 187 109 0 0
WeakHashMap 156 250 47 31 0 16
ConcurrentHashMap 94 140 79 46 0 16

结论：

1、HashMap的性能比较高，但不是线程安全的

2、ConcurrentHashMap的put性能没有HashMap的高，get的性能与HashMap一样或者略高于，但是是线程安全的